Method of inhibiting corrosion



0.1. Rises; JR I 2,856,358

METHOD 0: INHIBITINQ CORROSION Filed May 2, 1955 2 Sheets-Sheet 1 FIG. 1

INVENTOR. OLEN L. RIGG$.JR.

By @JM A T TORNE Y Get 14, 1958 o. 1.. RlGG syJR METHOD OF INHIBITING CORROSION Filed May 2, 1955 2 t e m s t e m S 2 FIG. 2

4 ORNEY 2,856,358 ME'II-IODOF ml-lmlTlNG coRuosroN Application May 2, 1955, Serial No. 505,4-a9 9 Claims; (or; 252-8155 This invention relates'to retarding or the prevention of corrosion in oil Wells and connecting pipe lines in intermediate storage to the refinery for crude oil. More pt zrticu'larly, I have found that an oil-soluble substituted gl'yoxalidine; also known as imidazoline salt of an alkaryl sulfonic acid, when added to well fluids in minor proporti'ons' acts to inhibit the rusting or corrosion of the metallic equipment used in the well due to hydrogen sulfide and c'arbondioxide environments.

Considerable corrosion takes place in the metallic equipment of practically all oil wells and in certain environments, corrosion may reach costly proportions. For example, casing, tubing, sucker rods, and lead lines are particularly subject to corrosion. The sucker rods and j'sucker rod boxes which operate under heavy cyclic load conditions areespecially susceptible to failure through corrosion" fatigue. As a' result of corrosion, costs of operations arev greatly increased because of the necessity of" pulling 'tubing'andsucker rods for repair or replace ment'." In addition, indirect costs in terms of production glosses v'vhileh'shut down for repair or replacement are It is, therefore, aprincipal' object-of this invention to provide a method of preventing corrosion in oil wells which is effective and-economical. myinvention is toprovide a substance which can be -added-to theoil well which will control corrosion and particularly willreduce pitting without any adverse effects onthecrudeoil. Other objects and advantages will be ap'parent from the following description.

hr 'briefi lhave discovered that' the addition of a minute qua 'ntity 'of l a' substituted'glyoiralidine salt of an alkaryl 'sulfonic' Cid to an oil well containing fluids which' 'c'ause corr sion is'effective in inhibiting or prevt'itin'g corr'osion of'the metal exposed to such fluids.

"*l have f'eund thatj the corrosive effects of the fluids on metallic sartaces can be substantially reduced and in many cases practically eliminated-by the introduction of an-"exc'eedinglystnall quantity of an oil-soluble substititted glyortalidine salt of an alkaryl sulfonic acid-into the well. I The particular substitutedglyoxalidines or imidazolines useful in my invention are hydroxy compounds. The inhibitor may be'add ed' to'the' well fi'uidsby' any conventional method; usually, by merely injecting the desired amount of the, inhibitorinto the well. As another method'of introducing-the inhibitor-"into the well, a tubing of relatively small diameter may be run down the center of the production tube of the well to approximately the bottom end thereof'an'd a. solution of. the inhibitor may be; pumped through the smalldiameter'tubingi so as'to enter the well stream near the bottorrrof the welltube. Therisingturbulen-tflow will thencarry the injected inhibitor up through the tube. Obviouslythe'corrosioninhibitor maybe added. or introduced into the well-by other means or methods depending in part on whetherthe wells are operated through. the easing or through tubing disposed in such casings; Also, it is clear. that. the inhibitors may be introduced into the top of the Well and allowed" to Another object of flow down or may be forced through any given point or points in the well at which the inhibitor then can come in contact with the turbulent up-going fluid mixture which, as stated, would cause metal corrosion but for the presence of the corrosion inhibitors of this invention. The effective and preferred proportions of my inhibitor are in the range approximately 2 to 500 and 25 to parts per million of well fluid respectively; namely, crude oil in brine. After separating the brine from the crude oil, the resulting crude oil exhibits favorable corrosion inhibiting properties when transported through connecting pipe lines to the refinery.

The corrosion inhibitors of this invention may be introduced into the system as such or they may be dissolved in a suitable solvent such as mineral oil, crude oil, kerosene, gasoline, organic esters, alcohols, ket-ones, or even water. Although any solvent which is nonreactive with the corrosion inhibitor may be employed, kerosene or a light hydrocarbon fraction is preferred as the particular solvent. When a solvent is used, it is preferred to use a concentration of corrosion inhibitor varying from about 25 to 40 percent. I

The substituted imidazolines useful in my invention are l-hydroxy-alkyl-Z-long chain alkyl imidazoline having the general formula:

wherein R is an alkyl radicalcontaining-from -11 to 17 carbon atoms, and R and R" are either the same or different: and are selected from the group consisting of hydrogen and an alkyl group having from about 6 to30 carbon atoms and'x is an integer varying from 1 p03. If both R and R" are alkyl groups, the total number of carbon atoms in those groups'would vary from 12 to 18. l-hydroxy-alkyl-Z-long chain alkyl imidazolines are prepared by reacting a monocarboxylic acid or ester with a diamine 'containinga hydroxy group at an elevated temperature, generally in the range of about 230 or higher at which temperature water is evolved and ring closure effected. Specific instructions for preparing these compounds are given in U. S. Patent 2,267,965 issued December 30, 1941,10 Alexander L. Wilson,and by Hofrnann, Journal of Organic Chemistry 12, 577 (1947). M

Suitable l-hydroxyalkyl-2=long chain alkyl imidazolines for use in the'improved' corrosion inhibitorsof this invention may be prepared by the reaction-of alon g'chain fatty acid for ester and a'hydroxyalkylethylene-diamine. Long chain fatty acids suchas lauric acid; 'tr-idecanoic acid, myristic-acid,-oleicacid,-stearic acid,- palmitic acid, linoleic acid, lin-olenicacid,-erucic acid, tall oil'fatt'y acid, oxidized petroleum wax fractions, acid numeridized oxo reaction products-,--etc; ,7 v I Hydroxyalkyl ethylene diarni-nes- With which the: long chain fatty acid 'may be reacted-to yield substitu'ted imidazolines suitable'forthisinvention-include:- hydroxyrriethyl ethylene diamine, hydroxyethyl ethylene diar'nine'gand the various 'hyd-roxy pr-opyl 'ethy-lene diamine's such as 1(3-hydroxypropyl) ethylene diarnine, 1(2-hydroxypropyl): ethylene diamine, and (Z-hydroxypropyl) ethylene in A v The preparation of 1 -hydroxyalkyl-2 -long chain alkyl imidazolines is exemplified-by thereaction; between stearic acid and hydroxyethyl ethylenediamine. By heating at 250 0, one mole of stearic acid with one moleof hydroxyethyl ethylene diamine, two moles of water are liberated and 1-hydroxyethyl-2-heptadecyl imidazoline is formed in accordance with the equation:

Examples of other 1-hydroxyalkyl-2'long chain alkyl imidazolines include:

l-hydroxymethyl-Z-undecyl imidazoline, l-hydroxyethyl-Z-undecyl imidazoline 1-hydroxypropyl-2-undecyl imidazoline l-hydroxyethyl-Z-dodecyl imidazoline 1-hydroxymethyl-2-tridecyl imidazoline 1-hydroxymethyI-Z-heptadecenyl imidazoline l-hydroxyethyl-2-heptadecenyl imidazoline 1-hydroxypropyl-Z-heptadecenyl imidazoline 1-hydroxymethyl-Z-heptadecyl imidazoline 1-hydroxyethyl-2-heptadecyl imidazoline l-hydroxyethyl-Z-pentadecyl imidazoline 1-hydroxypropyl-2-pentadecyl imidazoline 1-hydroxyethyl-2-heptadecadienyl imidazoline Suitable alkarylsulfonic acids are thosejobtained by the sulfonation of alkaryl hydrocarbons, which in turn are produced by the alkylation of an aromatic hydrocarbon such as benzene, toluene, xylene, cumene, and similar aromatic hydrocarbons. Straight or branched chain olefins, alcohols, or halides having from about 6 to about 30 carbon atoms and preferably from about 12 to about 18 carbon atoms are used as the alkylating agents. As to the olefins, those may be obtained by the polymerization of low molecular weight olefins such as ethylene, propylene, and mixtures thereof or may be obtained by the cracking or hydroforming of hydrocarbons such as wax, kerosene, or other petroleum fractions. Suitable alkaryl sulfonic acids for use in my invention are those having molecular weights within the range of about 400-550. These acids are obtained by sulfonating alkaryl hydrocarbons of the proper molecular weight. A particular useful sulfonic acid is postdodecylbenzene sulfonic acid which is obtained by sulfonating the de-' tergent alkylate known as postdodecylbenzene. Postdodecylbenzene consists of monoalkylbenzenes and dialkylbenzenes in the approximate ratio of 2:3. Its typical physicalproperties are as follows:

Specific gravity at 38 C 0.8659

Average molecular weight 365 Percent sulfonatable 88 A. S. T. M., .D-158 Engler:

I. B; P F-.. 647 F- 682 50 F..- 715 90' PL. 760 95 F... 775 F. B. P "F... 779 Refractive index at 23 C 1.4900

Viscosity at: 1

---1() C centipoieec 2800 280 40 do 78 80 C do 18 Aniline point C-.. 69 Pour point 1 25 In addition to the sulfonic acid obtained by sulfonating postdodecylbenzene, other alkaryl sulfonic acids have been used wherein the molecular weightof the acid has varied. from about 320 to overtSOO. Dode'cylbenzene sulfonic acid and diwaxbenzene sulfonic acidare eic amples of acids having molecular weight of 320 and over 600 respectively. The molecular weight of diwaxbenzene sulfonic acid is approximately 630 and is obtained by alkylating benzene with chlorowax.

The alkaryl hydrocarbons so obtained may be sulfonated by any conventional sulfonating method which pro cedures are well known to those skilled in the art; however, I prefer the method disclosed in the co-pending application entitled Method of SulfonatingAlkyl Aromatic Hydrocarbons, by Luntz and Popovac, filed December 8, 1953, Serial No. 396,822, now U. S. Patent 2,768,199, which disclosure is made a part of this application. l A

Following the production of the sulfonic acid as described above, the salt may beformed by mixing equal molecular proportions of the imidazoline with the alkaryl sulfonic acid. The imidazoline may be added to the sulfonic acid or conversely the sulfonic acid may be added to imidazoline. The reaction is generally very rapid and as a consequence the reactionislOO percent complete by the time the components are mixed, however, if necessary external heating or cooling may be employed for an additional time to complete the reaction. i i H In addition to the uses enumerated above, myinhibitors may be used efiectively to inhibit corrosion in tankers carrying crude oil or refined petroleum products. They are also valuable in preventingcorrosion of pipe line carrying either crude oil or petroleum refined products.

In order to disclose the nature of the present invention still more clearly the following illustrative examples will be given. It is to be understood, however, that the invention is not to be limited to the, specific conditions or details set forth in these examples. except in solffar as such limitations are specified in the appendedclaims. Partsgiven are parts by weight. j Y

l The 'efiiciencies of thefvarious inhibitors werefdetermined both in hydrogen sulfide and carbon dioxide environments. The methods used are as. described under Procedures A and B below. i I

PROCEDURE A Efficiencies of corrosion inhibitors in a hydrogen sulfide environment were compared by determining the, percent protection given a mild carbon steel testacoup0n-subjected to corrosive conditions in the presence-of the'zcorrosion inhibitor in theequipment illustrated .in Fig.1. A large-mouth bottle of about,25,0 ml. capacity was charged with 150 ml. of Arbuckle brine and'tSO-mlL of kerosene containing the corrosion inhibitonbeing tested. The bottle was agitated to distribute. the corrosion inhibitor between the two phases, aweighed l-inch by, 3

inch 10-20 mild carbon steel coupon inserted, andbottle stopper fitted on. Hydrogen sulfide was bubbled through the solution at a rate of about 12 ml. per second. After about 18 hours, the coupon was removed from the bottle, descaled by scrubbing witha nylon bristle brushand a cleaning powder, weighed and its loss in Weight determined. The same technique was followed to obtain a blank inthe absence of corrosion inhibitor. The percent protection was calculated as follows:

P.C.P.= x

of coupon subjected to test in presence assass n PROCEDURE B E uipment suitable for determination of corrosion in an atmosphere of carbon dioxide is shown'dn Fig. 2. Vc'sse'l A is equipped with a mdtor' D for rotating a coupon holder C holding coupon P. Provisions B and E provide for introducing and exhausting carbon dioxide that has been metered in flow meter -F and saturated with Water vapor in wettin'g'vessel G. H is a' thermometer for indicating the temperature of the fluids undergoing test and J is a means for wihdrawing samples of fluid undergoing test. Q is a vessel attached to the glass jar A and i's provided with'a screw cap R. Ve'ss'el' Q fits over trap door S; The purpose of this vessel'is for inserting the coupon Pinto the glass 'jar A. T indicates a bearing through which the shaft of motor D passes. Pump 'sup- .plies means for maintaining immiscible fluids in dispersed state. Corrosion rate in units of mil penetration per "year is calculated as follows:

where:

M. P. Y.=mils p'enetration'per year;

W,=initial weight of coupon in grams.-

W;=final weight of coupon in grams.

g=spe'cific weight of coupon in grams per cubic inch. A=areaof coupon in square inches.

tfiduration -of corrosion test in years.

' The present invention may be clearly understood from the following examples which are given -by way of illustration only and are not intended to be considered as a limitation of the invention.

Example 1 in which R is undecyl, heptadecenyl, and heptadecyl and molecular weights are 276, 355, and 360, respectively, was added to one molecular weight of postdodecylbenzene sulfonic acid having a molecular weight of 440 and Obtained by the sulfonation of the still bottoms remaining after distilling the alkylation product of benzene with tetrapropylene up to 205 C. at mm. pressure. The 1-hydroxyethyl-2-long chain alkyl imidazoline polydodecylbenzene sulfonate obtained was tested as a corrosion inhibitor in accordance with Procedure A. The results are given in the following Table 1.

TABLE 1.PERCENT PROTECTION OFFERED BY VARIOUS CONCENTRATIONS OF IMIDAZOLINE SULFONATES Imidazoline Sulionate Salt Concentration-p. p. m.

Imidazoline sulfonic Acid 5 10 50 100 PDBSOaH 76 84 91 91 91 PDBSOaH 70 71 88 90 96 PDBSOaH 86 92 94 95 97 1 Postdodecylbenzene sulfonic acid having molecular weight of 440.

Example 2 The substitution of other alkyl aromatic sulfonic acids having a molecular weight of about 400 to about 550 for the postdodecylbenzene sulfonic acid of molecular weight 440 used in Example 1 gives salts offering corrosion inhibition of the same order as the salts listed in Table 1.

Example 4 On substitution of diwaxbenzene sulfonic acid of'molecular weight 630 and obtained by alkyla'ting benzene with'chlorowax for postdodecylbenzene in Example 1, a salt was obtained with Amine S which gave about SOpercent protection at '100 p." p. in. concentration.

Example 5 One molecular weight of Amine 2'30, a product of Carbide and Carbon Chemical Company and being 1'- aminoe'thyl-Z-heptadecyl imidazoline 'was added to molecular weight of postdodecylbenzene sulfonic acid and dodecylbenzene sulfonic acid. The salts obtained were tested as a corrosion inhibitor in accordance with Procedure A. The results are given in Table 2.

TABLE 2.--PEROENT PROTEOTIONOFFERED BY'VARIOUS CONCENTRATIONS OF -1AMINOETHYL IMIDAZOLINE SULFONATES Imidazoline Sulfonat'e Salt Concentration-p. p. m'.

Imidazoline 'Sulfon'ic Acid 5 V 10 2'5 50' 100 Amine 230 PDBSOaH 36 e3 76 7s 83 Amine 230 DBSO3H2 4 4s 59 59 70 1 Postdodecylbenzene sulfonic acid. Dodecylbenzene sulfonic acid.

Examples 1 to 5 were repeated except that the corrosion tests were conducted in a carbon dioxide environment in accordance with Procedure B rather than in a hydrogen sulfide environment. The results obtained as to the amount of protection afforded by the imidazoline derivatives in the carbon dioxide environment were similar to that afiorded in the hydrogen sulfide environment. Examples 1 and 2 were repeated with the exception that the corrosion tests were conducted in an environment comprising both carbon dioxide and hydrogen sulfide. The protection afforded by the imidazoline derivatives in the presence of the two gases was excellent.

A comparison of the data of Tables 1 and 2 show that of the substituted imidazoline salts those prepared from the l-hydroxy-alkyl-Z-long chain alkyl imidazolines are more effective as inhibitors than those prepared from the l-amino-alkyl-2-long chain alkyl imidazolines. Examples 1, 2, 3, and 4, show that the salts formed from alkaryl sulfonic acids having a molecular weight within the range of 400-650 are more effective as inhibitors than those prepared from alkaryl sulfonic acids having molecular weights outside that range.

What is considered new and inventive in the present invention is defined in the hereunto appended claims, it

being of course understood that equivalents known to those skilled in the art are to be construed as within the scope and purview of the claims.

I claim:

1. The method of inhibiting corrosion of ferrous metals in contact with corrosive fluids which comprises the addition to said corrosive fluids of an amount within the range of 2 to 500 parts per million of the corrosive fluids contacted an oil-soluble salt, said salt being the reaction product of l-hydroxy-alkyl-Z-long chain alkyl imidazoline and an alkaryl' sulfonic acid wherein the alkaryl sulfonic acid has a molecular weight within the range of about 400 to 550.

2. The method of inhibiting corrosion of ferrous metals in contact with corrosive fluids which comprises the addition to said corrosive fluids of an amount within the range of 25 to 100 parts per million of the corrosive fluids contacted an oil-soluble salt, said salt being the reaction product of l-hydroxy-alkyl-Z-long chain alkyl imidazoline and an alkaryl sulfonic acid whereinthe alkaryl sulfonic acid has a molecular weight within the range of about 400 to 550.

3. The method of claim 1 wherein the corrosive fluids contain carbon dioxide.

4. The method of claim 1 wherein the corrosive fluids contain hydrogen sulfide.

5. The method of inhibiting corrosion of ferrous metals in contact with corrosive fluids which comprises and an alkaryl sulfonic acid wherein the alkaryl sulfonic sulfonic acid has a molecular weight Within the range of I about 400 to 550.

7. The method of inhibiting corrosion of ferrous metals in contact with corrosive fluids which comprises the addition to said corrosive fluids of an amount within the range of 2 to 500 parts per million of the corrosive 'fluidseontactedan oil-solublesalt, said salt being the reaction product of 1'-hydroxyethyl-2-heptadecyl imidazoline and an alkaryl sulfonic acid wherein the alkaryl sulfonic acid has a molecular weight within the range of about ,400,to 550. A

8. The method of claim 1 wherein the alkaryl sulfonic acid is postdodecylbenzene sul'fonic acid.

9; The method of inhibiting corrosion of ferrous metals in contact with corrosive fluids containing carbon dioxide andv hydrogen sulfide which comprises the addition to saidcorrosive fluids of an amount within the range of 2 to 500 parts, per million of the corrosive fluids contacted an oil-soluble salt, said salt being the reaction product of l-hydroxy-alkyl-il-long chain alkyl imidazoline and an alkaryl sulfonic acid wherein, the alkaryl sulfonic acid has a molecular weight within the range of about 400 to 550.

References Cited in the file of this patent UNITED STATES PATENTS Shock et a1. Mar. 12, 

1. THE METHOD OF INHIBITING CORROSION OF FERROUS METALS IN CONTACT WITH CORROSIVE FLUIDS WHICH COMPRISES THE ADDITION TO SAID CORROSIVE FLUIDS OF AN AMOUNT WITHIN THE RANGE OF 2 TO 500 PARTS PER MILLION OF THE CORROSIVE FLUIDS CONTACTED ON OIL-SOLUBLE SALT, SAID SALT BEING THE REACTION PRODUCT OF 1-HYDROXY-ALKYL-2-LONG CHAIN ALKYL IMIDAZOLINE AND AN ALKARYL SULFONIC ACID WHEREIN THE ALKARYL SULFONIC ACID HAS A MOLECULAR WEIGHT WITHIN THE RANGE OF ABOUT 400 TO
 550. 